KR20070064490A - Adative cruise control system for vehicle and method thereof - Google Patents

Abstract

An adaptive cruise control system for a vehicle and a method thereof are provided to achieve stability and reliability for the operation of the system by computing a maximum deceleration and a minimum safe following distance. The adaptive cruise control system for a vehicle includes a brake gain detecting portion, a horizontal shaft active force detecting portion(11), a vertical shaft active force detecting portion(12), a friction coefficient computing portion(13), a tire dynamic radius detecting portion(14), a wheel angular velocity detecting portion(15), a vehicle speed detecting portion(16), a slip computing portion(17), a slip inclination computing portion(18) and a maximum friction coefficient computing portion(19). The maximum friction coefficient computing portion(19) estimates a maximum friction coefficient between a road surface and a tire according to an initial inclination of a slip and a friction coefficient and applies it to the adaptive cruise control.

Description

Vehicle distance control system and its control method {ADATIVE CRUISE CONTROL SYSTEM FOR VEHICLE AND METHOD THEREOF}

1 is a block diagram illustrating a system for controlling a distance between vehicles in accordance with the present invention.

2 is a diagram illustrating a relationship between the horizontal axis force estimation in the vehicle inter-vehicle distance control system according to the present invention.

3 is a flowchart of an embodiment of performing inter-vehicle distance control in a vehicle according to the present invention.

4 is a diagram showing the relationship between the maximum friction coefficient estimated when driving from a wet road surface to a dry road surface according to the present invention.

5 is a diagram illustrating a relationship between a maximum friction coefficient according to various road surface conditions.

<Explanation of symbols for the main parts of the drawings>

10 brake gain detector 11 horizontal force acting detector

12: vertical axis force detection unit 13: friction coefficient calculation unit

14: tire companion diameter detection unit 15: wheel angular velocity detection unit

16: vehicle speed detection unit 17: slip calculation unit

18: slip slope calculation unit 19: maximum friction coefficient calculation unit

The present invention relates to an inter-vehicle distance control system mounted on a vehicle, and more particularly, to calculate a maximum deceleration and a minimum safety distance by estimating a maximum friction coefficient between a road surface and a tire, and a time gap for a minimum safety distance. It relates to an inter-vehicle distance control system and a control method thereof in a vehicle to limit the control.

According to the rapid spread of automobiles, statistics show that the road network is growing much faster than the expansion speed.

Therefore, as the risk of collision between vehicles on the road increases day by day, various intelligent safety systems have been developed and applied by combining the consumer's desire for a more stable and intelligent vehicle with the development trend of the automobile related industry.

In particular, many studies on collision warning and avoidance between the own vehicle and the preceding vehicle have been conducted. Accordingly, the inter-vehicle distance control system ensures a safer and more comfortable driving environment in a complicated road situation.

However, since there is no definite answer about the time and method of collision warning and avoidance, a lot of studies and tests are in progress.

When the distance control system sets the speed at which the driver wants to drive, the control means analyzes various load conditions and the vehicle speed on the vehicle to control the throttle actuator and the brake actuator to maintain driving at the set speed.

Then, a time gap that can maintain a safe driving distance is set.

As described above, in the process of driving the vehicle at a constant speed, the control unit detects a distance between the preceding vehicle through a distance detecting means installed at a predetermined position in front of the vehicle, and extracts the relative distance and the relative speed between the host vehicle and the preceding vehicle.

If the extracted relative distance and relative speed are in a state of relative distance and relative speed which are at risk of collision, distance control is performed by applying a set time gap.

The safe mileage is calculated under the condition of (time gap × own vehicle speed).

At this time, by arithmetically calculating the critical braking distance between the host vehicle and the preceding vehicle, the safe driving distance is ensured by controlling the braking through the brake actuator control or the engine torque reduction control through the throttle actuator control.

As described above, when the speed of the own vehicle is decelerated by the control for maintaining the safe driving distance, and thus the relative distance between the own vehicle and the preceding vehicle becomes far, the engine torque is restored through the throttle actuator control to recover the set constant speed traveling speed. do.

In the above-described conventional vehicle distance control system, a time gap for maintaining a safe driving distance is set in advance to a predetermined value, and thus it is impossible to adjust by the driver.

In addition, depending on the system, the driver can set the time gap in three stages (Far / Med / Close), but it is difficult to set the time gap during operation, and it is cumbersome to operate. Inhibits.

For example, if the set time gap is 2 seconds / 1.5 seconds / 1 second, when the host vehicle runs at 100 km / h, the vehicle runs at intervals of 55 m / 42 m / 28 m, respectively.

However, in the normal system, the time gap is set to the theoretical maximum deceleration of the own vehicle to be 9.8 kPa considering the friction coefficient between the tire and the ground is 1.0.

Therefore, when the above conditions are taken into consideration, for example, the minimum stopping distance of a vehicle traveling at 100 km / h becomes 38 m, and this distance is higher than the distance set by the driver (55/42/28 m) for the driver's safety. ).

However, it is necessary to consider that the coefficient of friction between the tire and the ground is not always 1.0.

The friction coefficient between the tire and the ground exhibits different characteristics depending on the state of the road surface as shown in FIG. 6.

In addition, this coefficient of friction varies greatly depending on the shape of the road surface (asphalt, concrete, unpaved road, etc.), the type of tire (carcass / radial), the shape of the tire tread and the degree of aging.

In other words, the difference in friction coefficient between driving new tires in dry weather and running concrete and running old tires in rainy weather is about twice the difference, so the maximum deceleration also doubles. Will be gone.

The inter-vehicle distance control system applied to the conventional vehicle has a maximum deceleration of 9.8 kPa under conditions where the tire's condition and the road surface's friction coefficient are not sufficiently reflected when calculating the driver's minimum safety distance in consideration of the maximum deceleration during driving. I am fixed and cannot secure the optimum safety distance.

Therefore, there is a disadvantage that collision between the preceding vehicle and the own vehicle cannot be avoided in an emergency situation.

The present invention has been invented to solve the above problems, the purpose of which is to calculate the maximum deceleration and minimum safety distance by estimating the maximum friction coefficient between the road surface and the tire, the time gap (Time Gap) according to the minimum safety distance By limiting control, it is to provide stability and reliability to the operation of the system.

That is, when there is no preceding vehicle, the vehicle runs at a constant speed at a speed set by the driver, and when there is a preceding vehicle, the vehicle is driven by following the preceding vehicle while maintaining a minimum safety distance.

According to an aspect of the present invention, there is provided an inter-vehicle distance control system, comprising: a brake gain detector for extracting a brake gain from a wheel speed and a brake pressure of each wheel; A horizontal axis acting force detector for detecting an acting force acting on the tire of each wheel from the brake gain and the shift stage torque; A vertical axis force detection unit for detecting an action force acting as a vertical axis on the tire of each wheel by calculation considering the total weight of the vehicle and the dynamics of the vehicle; A coefficient of friction calculation unit for calculating a coefficient of friction between the road surface and the tire from the relationship between the force acting on the tire of each wheel and the acting force acting on the vertical axis; A tire companion diameter detecting unit for detecting a companion diameter of the tire which is a distance between the center axis of the wheel and the road surface from an action force acting as a vertical axis on the tire of each wheel; A wheel angular velocity detector for detecting a wheel speed of the wheel from the angular speed of each wheel; A vehicle speed sensor mounted on a transmission output shaft, the vehicle speed detecting unit detecting a current traveling vehicle speed from an output shaft rotation speed; A slip calculation unit for detecting a slip ratio at each wheel by calculating a wheel speed of each wheel and information of a current vehicle speed and a tire companion diameter through a set algorithm; A slip slope calculator for analyzing a slip coefficient between a road surface and a tire applied by a friction coefficient calculator and a slip ratio of each wheel applied by a slip calculator through a set algorithm; It provides a vehicle-to-vehicle distance control system comprising a maximum coefficient of friction calculation unit for estimating the maximum coefficient of friction between the road surface and the tire according to the initial slope of the slip and friction coefficient to apply to the distance control.

In addition, the present invention is a process for setting a time gap that can ensure a safe driving distance between the preceding vehicle and the vehicle with respect to the set speed when the driving speed is set in the driving state in which the inter-vehicle distance control system is operated; Detecting road surface and tire condition information under a current driving condition; Estimating a maximum friction coefficient between the road surface and the tire according to the road surface and the tire condition; Calculating a maximum deceleration rate by applying the estimated maximum friction coefficient; Calculating a minimum safety distance according to the maximum deceleration to limit and correct a time gap set at the time of setting the traveling speed; Recognizing a vehicle ahead and extracting a relative distance between the own vehicle and the preceding vehicle; Decelerating the vehicle speed by time gap control at the same time when the extracted relative distance is included within the minimum safety distance; If the vehicle does not exist in front of the driving includes a process for controlling the distance between the vehicle, characterized in that it comprises the step of maintaining the traveling speed set by the throttle actuator operation control.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating a system for controlling a distance between vehicles in accordance with the present invention.

As shown in the figure, the brake gain detector 10, the horizontal force acting force detector 11, the vertical axis acting force detector 12, the friction coefficient calculator 13, the tire companion diameter detector 14, the wheel angular velocity detector 15, the vehicle speed The detector 16, the slip calculator 17, the slip slope calculator 18, and the maximum coefficient of friction calculator 19 are configured.

The brake gain detector 10 extracts the brake gain K _B from the wheel speed detected from the wheel speed sensor mounted on each wheel FL, FR, RL, RR and the brake pressure acted by the brake actuator. Information is applied to the friction coefficient calculating unit 13.

The horizontal axis force detection unit 11 detects the force acting on the tire of each wheel FL, FR, RL, RR on the wheels from the applied brake gain K _B and the shift stage torque T _S , and provides information about it. Output

The acting force F _t acting on the horizontal axis is estimated by the torque T _S at the current shift stage and the brake gain K _B as shown in FIG. 2, and the torque T _S at the current shift stage. Is calculated by the torque T _t and the wheel speed of the torque converter.

The torque T _t of the torque converter is calculated by the engine torque T _net extracted from the engine map, the carrier speed and the gear state (shift stage) according to the throttle opening degree and the engine speed.

The brake gain K _B is calculated from the brake pressure acting on each wheel FL, FR, RL, RR by the brake actuator and the speed of each wheel.

The vertical force acting force detection unit 12 acts as a vertical axis on the tires of each wheel FL, FR, RL, RR by calculating the total weight of the vehicle including the cargo loaded on the vehicle, the number of people on board, and the dynamics of the vehicle. The force acting on the detected force is applied to the friction coefficient calculating unit 13.

The friction coefficient calculating unit 13 calculates the friction coefficient between the road surface and the tire from the relationship between the acting force acting on the tire of each wheel and the acting force acting on the vertical axis, and applies the information about the friction coefficient to the slip slope calculating unit 18.

The tire companion diameter detecting unit 14 detects a companion diameter of a tire that is a distance from a road surface based on the center axis of the wheel from an action force acting as a vertical axis on the tires of the wheels FL, FR, RL, and RR. Information is applied to the slip calculation unit 17.

The wheel angular velocity detection unit 15 is a wheel speed sensor mounted on each wheel, and detects the speed of the corresponding wheel from the angular speeds of the respective wheels FL, FR, RL and RR, and provides information on the slip calculation unit 17. To apply.

The vehicle speed detection unit 16 is a vehicle speed sensor mounted on the transmission output shaft. The vehicle speed detection unit 16 detects the current traveling vehicle speed from the output shaft rotational speed, and applies information about the same to the slip calculation unit 17.

The slip calculating unit 17 detects a slip ratio of each wheel by calculating algorithms of the speed of each wheel, the information of the current vehicle speed, and the tire accompanying diameter through a set algorithm, and sends the information about the slip ratio to the slip slope calculating unit 18. Is authorized.

The slip slope detecting unit 18 analyzes the friction coefficient between the road surface and the tire applied by the friction coefficient calculating unit 18 and the slip ratio of each wheel applied by the slip calculating unit 17 through a set algorithm to slip slope. Detect and output information about it.

The maximum coefficient of friction calculation unit 19 estimates the maximum coefficient of friction between the road surface and the tire according to the initial slope of the slip and the coefficient of friction so that the information is applied to the distance control.

The maximum coefficient of friction calculation unit 19 uses the relationship between the slip and the coefficient of friction, the friction coefficient increases so as to increase the slip of the tire, but decreases again when the slip is excessive, the maximum between the road surface and the tire Estimate the coefficient of friction.

Typically, in the case of dry road surface, the maximum coefficient of friction is 1.0, and the maximum deceleration in this condition is determined by Equation 1 and set to 9.8 m / s ² .

Deceleration = coefficient of friction × acceleration of gravity

An operation of controlling the inter-vehicle distance by estimating the maximum friction coefficient between the road surface and the tire in the present invention including the above-described function will be described with reference to FIG. 3.

When the driver sets the speed to drive at constant speed in the driving state in which the inter-vehicle distance control system is operating (S101), the inter-vehicle distance control system is a condition of dry road surface having a maximum friction coefficient of 1.0 for the speed set by the driver. On the basis of this, a time gap for securing a safe driving distance between the preceding vehicle and the host vehicle is set (S103).

Thereafter, as the vehicle travels, information on the road surface and tires mounted on each wheel is detected (S104).

The tire information is obtained from each wheel FL from the brake speed K _B and the shift stage torque T _S extracted from the wheel speed for each wheel FL, FR, RL, RR and the brake pressure actuated by the brake actuator. (FR, RL, RR) From the force acting on the horizontal axis of the tire, the total weight of the vehicle and the dynamics of the vehicle From the information on the acting force acting on the tire of each wheel (FL, FR, RL, RR) and the vertical actuation force Companion diameter information of the tire, which is a distance from the road surface, based on the center axis of the extracted wheel.

The road surface information is mounted on a speed and transmission output shaft of each wheel FL, FR, RL, RR detected by the wheel angular velocity detector 15 mounted on each wheel FL, FR, RL, RR. It includes information on the current running vehicle speed detected by the vehicle speed detecting unit 16, the speed of each wheel FL, FR, RL, RR, and the slip ratio of each wheel extracted from the information of the current running vehicle speed and the accompanying diameter of the tire. .

As described above, when the information on the road surface and the tires mounted on each wheel is extracted in S104, the maximum friction coefficient between the road surface and the tire according to the current road surface state and the tire state is estimated and applied to the inter-vehicle distance control system (S105).

The estimation of the maximum friction coefficient is performed as follows.

From the brake gain (K _B ) and the shift stage torque (T _S ), the force acting on the horizontal axis of the tire is detected, and the force acting on the vertical axis of the tire under the conditions of the total weight of the vehicle and the dynamics is detected. Calculate the friction coefficient.

Then, the wheel angular velocity detected at each wheel FL, FR, RL, RR and the slip ratio calculated from the current vehicle speed and the tire companion diameter are detected.

Thereafter, the slip slope is calculated from the calculated friction coefficient and the slip ratio to calculate the maximum friction coefficient.

The maximum coefficient of friction increases with increasing slip of the tire and is detected by specifying that the slip is excessive.

As described above, when the maximum friction coefficient between the road surface and the tire is calculated and applied to the inter-vehicle distance control system, the inter-vehicle distance control system calculates the maximum deceleration at the current vehicle speed according to the maximum friction coefficient between the road surface and the tire (S106). Calculate the minimum safety distance from the preceding vehicle (S107).

When the minimum safety distance is calculated as described above, the time gap set on the basis of the friction coefficient 1.0 at the time of setting the traveling speed is limited (S108).

That is, if the time gap is set based on the friction coefficient 1.0 of the road surface at the time of setting the driving speed of the driver, but the maximum friction coefficient according to the road surface and the tire state that is actually detected has a value less than or equal to the friction coefficient 1.0, The time gap set to is a state in which the minimum safety distance cannot be secured.

Therefore, the time gap is limited and corrected.

In the state in which the time gap is limited and corrected as described above, the preceding vehicle that is running in front is recognized (S109), and it is determined whether the vehicle exists (S110).

When the vehicle does not exist in the above state, the vehicle enters the speed control mode (S111) and maintains the driving at the speed set by the driver through the control of the throttle actuator (S112).

However, if there is a vehicle ahead of the driving ahead, the relative distance in consideration of the relative speed between the own vehicle and the preceding vehicle is extracted (S113) and it is determined whether the relative distance is included within the set distance, that is, the minimum safety distance (S114). .

If the relative distance is not included within the minimum safety distance in the determination of S114, the vehicle enters the speed control mode (S111) and maintains the driving at the speed set by the driver through the control of the throttle actuator (S112).

However, if the relative distance is within the minimum safety distance of the set distance in the determination of S114, there is a risk of collision in case of sudden braking of the preceding vehicle. It performs (S115).

Therefore, the braking control through the operation of the brake actuator or the engine torque reduction control through the operation of the throttle actuator allows the speed of the vehicle to be decelerated so that the relative distance between the vehicle and the preceding vehicle can be maintained while maintaining the minimum safety distance (S116). ).

For example, if the vehicle is traveling at 100 km / h, the minimum safety distance is about 38m on a normal road surface with a maximum friction coefficient of 1.0.However, if the tire is worn and wet, the minimum friction distance is calculated as 0.7. To increase.

Therefore, even if the driver had expected the time gap to be controlled to 1.5 seconds * own vehicle speed (100km / h) = 41m by setting the time gap to 1.5 seconds, the actual minimum safety distance was 56m, so the actual time gap was 100km / The calculation of h x x seconds = 56m limits the correction to 2.02 seconds to ensure a safe distance to prevent a minimum collision.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible.

As described above, according to the present invention, the maximum deceleration is calculated by real-time estimation of the maximum friction coefficient between the road surface and the tire according to the state of the road surface and the tire state, and thus the minimum safety distance according to the speed of the vehicle is calculated. The time gap is limited and compensated for the minimum safety distance.

In the present invention, when the relative distance with the preceding vehicle becomes smaller than the calculated minimum safety distance, the driver is alerted to the driver and at the same time, the automatic deceleration is performed, thereby actively controlling the driver's safety.

Claims (11)

In the inter-vehicle distance control system, A brake gain detector for extracting a brake gain from the wheel speed and the brake pressure of each wheel; A horizontal axis acting force detector for detecting an acting force acting on the tire of each wheel from the brake gain and the shift stage torque; A vertical axis force detection unit for detecting an action force acting as a vertical axis on the tire of each wheel by calculation considering the total weight of the vehicle and the dynamics of the vehicle; A coefficient of friction calculation unit for calculating a coefficient of friction between the road surface and the tire from the relationship between the force acting on the tire of each wheel and the acting force acting on the vertical axis; A tire companion diameter detecting unit for detecting a companion diameter of the tire which is a distance between the center axis of the wheel and the road surface from an action force acting as a vertical axis on the tire of each wheel; A wheel angular velocity detector for detecting a wheel speed of the wheel from the angular velocity with respect to each wheel; A vehicle speed sensor mounted on a transmission output shaft, the vehicle speed detecting unit detecting a current traveling vehicle speed from an output shaft rotation speed; A slip calculation unit for detecting a slip ratio at each wheel by calculating a wheel speed of each wheel and information of a current vehicle speed and a tire companion diameter through a set algorithm; A slip slope calculator for analyzing a slip coefficient between a road surface and a tire applied by a friction coefficient calculator and a slip ratio of each wheel applied by a slip calculator through a set algorithm; And a maximum coefficient of friction calculation unit for estimating the maximum coefficient of friction between the road surface and the tire according to the initial slope of the slip and the coefficient of friction and applying the same to the distance control. The method of claim 1, The shift stage torque is calculated based on the torque and the wheel speed of the torque converter. The method of claim 2, The torque of the torque converter is calculated by the engine torque, the carrier speed and the gear state (shift stage) extracted from the engine map according to the throttle opening degree and the engine speed. The method of claim 1, The wheel angular velocity detection unit is a vehicle inter-vehicle distance control system, characterized in that made of a wheel speed sensor mounted on each wheel. The method of claim 1, The maximum coefficient of friction calculator calculates the maximum coefficient of friction between the road surface and the tire by applying a characteristic that the slip coefficient increases to increase the slip of the tire and decreases again when the slip is excessive. A vehicle inter-vehicle distance control system, characterized in that for estimating. Setting a time gap for securing a safe driving distance between the preceding vehicle and the own vehicle with respect to the set speed when the driving speed is set in the driving state in which the inter-vehicle distance control system is operated; Detecting road surface and tire condition information under a current driving condition; Estimating a maximum friction coefficient between the road surface and the tire according to the road surface and the tire condition; Calculating a maximum deceleration rate by applying the estimated maximum friction coefficient; Calculating a minimum safety distance according to the maximum deceleration to limit and correct a time gap set at the time of setting the traveling speed; Recognizing a vehicle ahead and extracting a relative distance between the own vehicle and the preceding vehicle; Decelerating the vehicle speed by time gap control at the same time when the extracted relative distance is included within the minimum safety distance; If the vehicle does not exist in front of the driving ahead of the vehicle distance control method comprising the step of maintaining the driving speed set by the throttle actuator operation control. The method of claim 6, The time gap according to the setting of the traveling speed is set based on the condition of the dry road surface having a maximum friction coefficient of 1.0. The method of claim 6, The tire state information in the current driving conditions, An action force acting as a horizontal axis on each wheel tire from the brake gain and the shift stage torque extracted from the wheel speed and the brake pressure of each wheel; An action force acting as a vertical axis on each wheel tire by applying the total weight of the vehicle and the dynamics of the vehicle; And a companion diameter of the tire which is a distance between the center axis of the wheel and the road surface extracted from the vertical axis action force. The method of claim 6, The road surface condition information includes a speed of each wheel; Current vehicle speed; And a slip ratio of each wheel extracted from information of the speed of each wheel and the current running vehicle speed and the accompanying diameter of the tire. The method of claim 6, The maximum coefficient of friction is estimated, A method of controlling a distance between vehicles, wherein the friction coefficient increases so that the tire slip increases, and when the slip becomes excessive, the friction coefficient decreases again to estimate the maximum friction coefficient between the road surface and the tire. The method of claim 6, The time gap limit correction is, A method of controlling the distance between vehicles of a vehicle, characterized by correcting a friction coefficient of 1.0 based on a dry road surface to a value that ensures a minimum safety distance according to a maximum friction coefficient between a current road surface and a tire at a time of setting a driving speed.

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